Fibrous Adhesive Entrapment of Lumbosacral Nerve Roots As a Cause of Sciatica

Original Article

Fibrous adhesive entrapment of lumbosacral nerve roots as a cause of sciatica

K Ido*,1 and H Urushidani1 1Department of Orthopaedic Surgery, Kurashiki Central Hospital, Okayama, Japan

Study design: Report of seven patients with ®brous adhesive entrapment of lumbosacral nerve roots as a cause of sciatica, whose radiographic ®ndings were negative and who experienced relief from sciatica immediately after the entrapment was released. Objectives: To describe a new clinical entity of ®brous adhesive entrapment of lumbosacral nerve roots with negative radiographic ®ndings. Setting: Orthopaedic department, Japan. Methods: Clinical evaluation and post-operative outcome in seven patients with entrapment of lumbosacral nerve roots because of ®brous adhesion con®rmed intraoperatively. Results: Radiographic examinations by magnetic resonance imaging &MRI), myelography, and computed tomographic &CT) myelography demonstrated neither disc herniations nor spinal stenosis in all seven patients, and dierential nerve root block was eective for relieving sciatica and low back pain.We con®rmed, intraoperatively, entrapment of the nerve root by ®brous adhesion, and all seven patients were relieved from sciatica and low back pain postoperatively. Conclusion: This study presented seven patients with sciatica caused by ®brous adhesive entrapment of lumbosacral nerve roots who underwent decompression and release of ®brous adhesion.Radiographic examinations, such as MRI, myelography and CT myelography, showed no compressive shadows and also dierential nerve root block was eective for its diagnosis.This study seems to be the ®rst report of patients with entrapment of lumbosacral nerve roots caused by ®brous adhesion, whose radiographic ®ndings were negative. Spinal Cord &2001) 39, 269 ± 273

Keywords: entrapment; lumbosacral spine; nerve root; ®brous adhesion; low back pain; surgery; MRI; myelography

Introduction Compression of lumbosacral nerve roots in association adhesion.The aim of this study was to determine the with intervertebral disc herniation and spinal stenosis eectiveness of dierential nerve root block for the usually causes sciatic pain.1,2 Radiographic examina- diagnosis and to emphasize the necessity of surgical tions, such as magnetic resonance imaging &MRI), decompression and release of ®brous adhesive entrap- myelography, and computed tomographic &CT) myelo- ment of the lumbosacral nerve roots. graphy, usually reveal ®ndings of compression in patients with disc herniations and/or spinal stenosis. Methods However, we sometimes encounter patients with sciatic pain whose radiographic examinations reveal neither In our unit, between 1985 and 1998, 1841 patients with lumbar disc herniations nor spinal stenosis. sciatica and low back pain required surgical interven- In this study, we describe the surgical management tion.In seven patients, entrapment of lumbosacral of a series of patients with sciatica whose lumbosacral nerve roots because of ®brous adhesion was con®rmed nerve roots were entrapped because of ®brous intraoperatively and decompressive surgery was required.The clinical data of the patients are summar- ized in Table 1.They comprised four women and three men, their average age at the time of operation was 43 *Correspondence: K Ido, Department of Orthopaedic Surgery, Kurashiki Central Hospital, 1-1-1 Miwa, Kurashiki-city, Okayama, years, and the average follow-up period was 7 years 710-8602 Japan and 2 months. Fibrous entrapment of nerve root K Ido and H Urushidani 270

Table 1 The summary of clinical data Interval from Low Aected Root Follow- onset to back nerve block Myelo- JOA score Case Age Sex up Cause surgery pain SLR root no. Outcome graphy CTM MRI Pre Post 1 20 M 14Y8Mo Sports 5Mo (+) 108 (+) left S1 1 eective n.p. n.p. n.p. 10 24 2 50 F 8Y11Mo (7) 4Mo (+) 458 (+) left L5 1 eective n.p. n.p. n.p. 12 24 3 39 F 8Y (7) 7Mo (+) (7) right L6 1 eective n.p. n.p. n.p. 16 24 4 44 F 7Y11Mo (7) 4Mo (+) 508 (+) right L5 1 eective n.p. n.p. n.p. 14 22 5 58 M 5Y9Mo (7) 1Y (+) 708 (+) right L5 2 eective n.p. n.p. n.p. 8 19 6 43 M 2Y11Mo Labor 1Y1Mo (+) (7) left L5 1 eective irregular n.p. n.p. 12 18 7 50 F 2Y (7) 5Mo (+) 408 (+) left L5 2 eective n.p. n.p. n.p. 15 27 M: male; F: female; Y: year; Mo: month; SLR: straight leg raising

Radiographic examinations one patient, however, slightly irregular shadow of the Initially, MRI was performed for all patients. Patients nerve root was observed. All the seven patients with negative ®ndings on MRI underwent myelography complained of sciatica accompanied by low back pain. and CT myelography in order to look for slight Five of the patients had no cause for the development compressive shadows caused by intervertebral disc of the symptoms. Two patients had a suggestive life- herniations which could not be detected by MRI, style history: a football player and a manual laborer. myelography and CT myelography. Dierential nerve None of the seven patients experienced previous root block using lidocaine was attempted at suspicious medical history of low back pain and sciatica. The levels of neurological symptoms to identify which nerve average interval between onset of the symptoms and root was aected and also to con®rm whether or not surgical intervention was 7 months, and seemed not to pain relief was obtained. In the patients without be dierent from that of lumbar disc herniations or remarkable ®ndings in MRI, myelography and CT spinal stenosis. The average age at the time of surgery myelography, the level of this nerve root block was was close to that of lumbar disc herniations, and was determined according to physical examination data, somewhat younger than spinal stenotic patients. such as pain, sensory de®cit, and motor weakness. Dierential nerve root block at suspicious symptomatic levels was eective for relieving both sciatic pain and low back pain in all seven patients. Intraopera- Surgery tively, we con®rmed entrapment of the nerve root by After exploring the spinous process and lamina, ®brous adhesion. All the seven patients experienced laminotomy was performed using an osteotome complete relief from sciatic pain and low back pain followed by unroo®ng of the symptomatic nerve root. immediately after we released the ®brous adhesion, and As neither disc bulging nor compression of the nerve the JOA scores improved in all seven patients soon after root and the dura because of spinal stenosis was the operation. During an average follow-up period of 7 observed, discectomy was not performed. Entrapment years and 2 months, no recurrence of sciatic pain of the nerve root by ®brous adhesion was con®rmed accompanied by low back pain was observed and the and exfoliated. Microsurgical manipulation was often JOA scores were unchanged. useful for precise observation. These procedures resulted in release of the nerve root and creation of space around it. Representative case presentation

Case 7: A 51-year-old woman with low back pain Clinical evaluation and left sciatica was admitted to our hospital. Physical Preoperative clinical symptoms and those soon after examination on admission demonstrated positive the operation were assessed using the criteria for the straight leg raising at 458 in the left side and JOA evaluation of low back pain treatment outcome score was 15 points. Dierential nerve root block using proposed by the Japanese Orthopaedic Association lidocaine at left L5 nerve root level was eective in (JOA) (maximum score: 29 points) which is commonly relieving both the leg pain and low back pain (Figure used in Japan (Table 2). 1). MRI and CT myelography showed no disc bulging at L4/5, and myelography demonstrated no abnormal Results shadow of left L5 nerve root (Figures 2 ± 4). After completing laminotomy at L4/5, ®brous adhesive Radiographic examinations by MRI, myelography and entrapment was observed. Careful detachment of CT myelography demonstrated neither disc herniations ®brous adhesion resulted in setting the nerve root free nor compression of the nerve root and the dura because and the patient was relieved from both sciatic pain and of spinal canal stenosis in any of the seven patients. In low back pain and JOA score increased to 27 points.

Spinal Cord Fibrous entrapment of nerve root K Ido and H Urushidani 271

Table 2 The criteria for the evaluation of low back pain treatment outcome proposed by the Japanese Orthopaedic Association (JOA)

I. Subjective symptoms (9 points) A. Low back pain a. none 3 b. occasional mild pain 2 c. frequent mild or occasional severe pain 1 d. frequent or continuous severe pain 0 B. Leg pain and/or tingling a. none 3 b. occasional mild sypmtoms 2 c. frequent mild or occasional severe 1 symptoms d. frequent or continous severe pain 0 C. Gait a. normal 3 b. able to walk farther than 500 m, even 2 though it results in pain, tingling, and/or muscle weakness c. unable to walk farther than 500 m, 1 because of leg pain, tingling, and/or muscle weakness d. unable to walk farther than 100 m, 0 because of leg pain, tingling, and/or muscle weakness II. Clinical signs (6 points) A. Straight leg raising test (including tight hamstrings) Figure 1 Dierential nerve root block using lidocaine of left a. normal 2 L5 nerve root was completely eective b308*708 1 c. less than 308 0 B. Sensory disturbances a. none 2 Discussion b. slight disturbances 1 The nerve roots in the lumbosacral region may be easily c. marked disturbances 0 compressed by intervertebral disc herniations and/or C. Motor disturbances spinal stenosis. Such mechanical compressions of the a. normal (grade 5) 2 nerve root may induce functional changes, such as b. slight weakness (grade 4) 1 sensory de®cit, motor weakness, and pain.1,3 Rydevik c. marked weakness (grade 3 ± 0) 0 reported that compression of the nerve root caused III. Restriction of ADL (14 points) structural damage to the nerve ®bers, and impairment ADL Severe Moderate No of intraneural blood ¯ow; i.e. ischemia, and formation restriction restriction restriction of intraneural edema.1,3 He also suggested that long- a. turn over while 0 1 2 standing intraneural edema may progress to ®brosis lying around the nerve root.1,3 Lundborg reported that nerve b. standing 0 1 2 root compression injury caused local myelin changes c. washing 0 1 2 and that increased endoneurial ¯uid pressure interfered d. leaning forward 0 1 2 e. sitting (about 1 h) 0 1 2 with intrafascicular capillary ¯ow and constituted a pathophysiological mechanism in nerve compression f. lifting or holding 4 heavy objects 0 1 2 injuries. Howe suggested that acute nerve root g. walking compression neuropathies were usually painless, 0 1 2 whereas chronic injury of the nerve root produced a marked increase in mechanical sensitivity.5 Smyth also IV. Urinary bladder function (76 points) reported that repeated or continued pressure on the a. normal 0 nerve root made the root hypersensitive and caused b. mild dysuria 73 sciatica.6 Furthermore, he suggested that postoperative c. severe dysuria* 76 reactionary ®brosis around the nerve root seemed to be *Incontinence, urinary retention sucient to cause persistent acute sciatica.6

Spinal Cord Fibrous entrapment of nerve root K Ido and H Urushidani 272

Figure 2 MRI showed no disc bulging at L4/5 Figure 3 Postero-anterior myelogram demonstrated no abnormality of left L5 nerve root

Malcolm reported that degenerative disc disease and due to ®brous adhesive entrapment which re¯ected protrusion might lead to compression of epidural veins radiographic ®ndings was not detected, but adhesion and suggested a signi®cant relationship between the of the nerve root and restriction on nerve root evidence for venous obstruction and perineural movement were observed. In a patient with slightly ®brosis.7 irregular shadow of the nerve root, nerve root On the other hand, several investigators have compression which was observed intraoperatively suggested that chemical in¯ammation or irritation can was more severe than the other six patients. We cause sciatic pain, and that these are important factors considered that the grade of adhesive ®brous rather than mechanical compression. In experiments entrapment was not correlated with compressive using dogs, McCarron proved that homogenized ®ndings on MRI, myelography and CT myelogra- autogenous nucleus pulposus injected into the lumbar phy. Furthermore, several investigators reported that epidural space caused chemical or immunologic gadolinium enhanced MRI was useful and quite in¯ammation of the neural sac.8 Marshall suggested eective for the diagnosis of postoperative perineural that chemical irritation of the nerve root in association ®brosis.10,11 However, this technique has not been with disc prolapse and subsequent endoneurial edema widely used for preoperative screening of perineural caused was responsible for acute sciatic pain.9 ®brosis. We consider that gadolinium enhanced MRI In the light of all these previous reports, we suggest might be necessary in the investigation of ®brous that mechanical compression and/or chemical irrita- adhesive entrapment of the nerve root. Dierential tion cause not only a decrease of blood supply and nerve root block is eective and necessary for the endoneurial edema, but also subsequent nerve root diagnosis of ®brous adhesive entrapment2 in patients constriction and entrapment of the nerve root by with negative radiographic ®ndings on MRI, myelo- circumferential ®brous adhesion. graphy and CT myelography. With regard to surgical Here, we should discuss the potential reasons for procedure, laminotomy and unroo®ng of the sympto- negative ®ndings on MRI, myelography and CT matic nerve root seemed to be a fairly invasive and myelography. In six patients without remarkable an over-indicated surgery. However, we selected this radiographic ®ndings, severe nerve root compression procedure because we felt that a simple epidural

Spinal Cord Fibrous entrapment of nerve root K Ido and H Urushidani 273

Conclusions This study presented seven patients with sciatica accompanied by low back pain caused by ®brous adhesive entrapment of lumbosacral nerve roots who underwent decompression and release of ®brous adhesion. MRI, myelography and CT myelography revealed neither disc herniations nor nerve root compression except for an irregular shadow in myelography detected in a patient. Dierential nerve root block using lidocaine was eective in identifying the symptomatic level and relieving both the sciatic pain and low back pain in all the seven patients. This is the ®rst report of patients with ®brous adhesive entrapment of lumbosacral nerve roots whose MRI, myelography and CT myelography showed negative ®ndings. We would like to emphasize that surgical decompression and release of the ®brous adhesion is necessary for the treatment of this condition and dierential nerve root block and gadolinium enhanced MRI are essential for its diagnosis.

References

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